In the past, it has been common to use incandescent lamps in wide area light fixtures for use in hazardous locations. One of the primary reasons favoring the use of incandescent lamps in such applications is that the only potential source for creating a spark is the terminal connections between the power cord and the light socket. The risk is minimal and the connections can be housed in a metal housing; and other precautions can be taken to minimize a potential hazardous occurrence. Moreover, by designing the interconnecting terminals to reduce the possibility of a spark, these designs have become more reliable through the years.
With the modem advent of improved light sources, particularly the introduction of metal halide and other high intensity discharge (i.e., HID) lamps, light production can be increased for the same electric power, but these lamps require use of ballasts and electronic excitation circuitry, increasing the risk of a spark. Thus, one cannot rely solely on the tried and reliable conventional simple terminal connections to reduce the hazard of a spark within the confines of a lamp fixture, and one must account for the possibility of arcing or sparks within the electronic circuitry energizing the lamp.
A portable hand lamp for hazardous locations using fluorescent lamps is disclosed in U.S. Pat. No. 5,594,304. While fluorescent lamps are suitable for hand lamp usage, they are not particularly suited for use as a "wide area" light--that is, one that can be hung in a location and transmit over a wide range area. Fluorescent lamps do not transmit as much light as HID lamps do for the same electrical power, and the light from fluorescent lamps is frequently focused by a reflector or the like, to concentrate the light to a localized area, not, for example, to light a room or large work area.
It is also important for commercial reasons to receive approval or listing with an independent testing organization, such as Underwriters Laboratories, for light fixtures for hazardous locations to assure potential users that safety precautions have been taken and to reduce insurance premiums for product liability. Heretofore it has been difficult, if not impossible, to achieve listing of portable HID light fixtures for hazardous locations with independent testing agencies because of the potential hazards.